Process and apparatus for drying damp sheet material



7, 1967 T. P. c. BREUERS ETAL 3,350,788

PROCESS AND APPARATUS FOR DRYING DAMP SHEET MATERIAL Filed March 22,1966 22 21 Figi 41 17 E "I 4 1B www' v. ,1 mil/4011111111114 INVENTORSTHEO I-VERKE HRETIEN BREUERS PETER ANTOON FRIESEN BY M,--M

ATTORNEY United States Patent 3,350,788 PRtICESS AND APPARATUS FORDRYING DAMP SHEET MATERIAL Theo Pierre Chretien Breuers, Venlo, andPeter Antoon Friesen, Tegeien, Netherlands, assignors to ChemischeFabrielr L. van der Grinten N.V., Venlo, Netherlands, a Dutchcorporation Filed Mar. 22, 1966, Ser. No. 536,381 Claims priority,application Netherlands, Mar. 24, 1965, 65-3,753 It) Claims. (Cl. 34-23)ABSTRACT OF THE DISCLOSURE Dampened sheet material, such as exposedphotocopy material to which a thin layer of liquid has been applied fordevelopment of the latent image, is dried effectively without eitherwrinkling or sticking in the apparatus by being transported and heatedbetween confronting surfaces, at least one of which is a soft hairysurface, of moving walls such as contiguous flights of endless beltsformed of material non-absorptive to moisture. A suitable belt is madeof nylon plush having hairs of .2.8 cm. in length.

This invention relates to a process and apparatus for drying sheetmaterials. It is of special value for drying the damp prints which areobtained by photocopying processes and will be described with particularreference to that use. Nevertheless it is to be understood that theprocess and apparatus is of utility in drying damp sheet materials ofOther types.

By photocopying processes is meant any method for the production of animage on radiation-sensitive copy material which employs a processingtechnique such that the prints initially obtained are in a dampcondition. Such processes include, for example, those based on silverhalide photographic materials (including materials for the silver saltdiffusion processes), those based on diazotype and diazotype transfermaterials, and those based on iron salt materials (e.g. blueprint).

In photocopying processes it is required in many cases to moisten thecopy material, e.g. for the development of the latent image obtained byexposure. The moistening liquid usually consists of water or of anaqueous solution of chemicals. The water furnishes the moist medium inwhich the desired reaction can take place and it also acts as a carrierfor uniformly distributing the chemicals dissolved therein over the copymaterial.

After being moistened, the copies are generally passed through a dryingapparatus, in which they are heated with the aid of heating elements.The rise in temperature thus caused in the material often has afavourable influence on the image formation, while simultaneously thewater evaporates, so that ultimately a dry copy is ob tained.

In general there is a tendency to dry the copies as quickly as possibleafter moistening. To this end the temperature used in the dryingapparatus is preferably high. However, without special provisions thetemperature can not be raised too much, inter alia because the liquidmust be prevented from evaporating so rapidly that the copy is alreadyentirely dry before the image formation is complete. Too rapid anevaporation may occur in the known apparatuses for drying damp copieswhichare frequently applied in photocopying processes and in which thecopies are passed along electrical radiators with the aid of open stringor belt systems.

Better results are obtained in apparatuses which are constructed in sucha way that the copies are indeed rapidly heated to a temperature atwhich the water evaporates, but which are moreover provided with meansfor preventing escape of the vapour. In these apparatuses the moistmedium is maintained longer, so that the image formation can becompleted. Some embodiments of apparatuses of this kind are known. Inone embodiment the copies are pressed against the wall of a heated drumwith the aid of a water-tight and vapour-tight belt which prevents theevaporating water from escaping from the copies. In another embodimentthe copies are moved forward through a narrow channel which is isolatedfrom the surroundings and which extends between the wall of a rotatingdrum and a heated plate mounted around the drum. Although in these knownapparatuses the copies are dried in the desired manner and the imageformation is entirely completed, they yet show defects. In the apparatusof the first-mentioned type the copies often become wrinkled or creased,because the belt holds the copy material firmly and thus preventsexpansion and shrinkage of the material owing to moisture and,temperature variations. In the other apparatuses the material may stickin the narrow channel.

It is an object of the present invention to provide a process andapparatus which avoids or minimises the foregoing defects.

According to the present invention there is provided a process fordrying damp sheet material which comprises passing the sheet materialbetween two walls which face one another, move in the same direction andtransport the sheet material, and heating the sheet material during itssaid passage, the said walls being formed of material of very lowvapour-absorbency characteristics, i.e., of material substantiallynon-absorptive to moisture, and at least one of the facing surfaces ofsaid walls being a soft hairy surface.

According to a further feature of the invention there is providedapparatus for drying damp sheet material which comprises two wallsadapted to be. moved in the same direction, and located to accommodatebetween their facing surfaces a sheet material and to transport the saidsheet material by such movement, the said walls being formed of materialof very low vapour absorbency characteristics and at least one of thefacing surfaces of said walls being a soft hairy surface, and means forapplying heat to sheet material located between said walls.

When damp photocopy material is passed through this apparatus, the waterpresent will indeed evaporate, but it will be trapped between the hairsof one of the walls or both, so that the moist medium, which is requiredfor the completion of the image formation, is maintained. Naturally thespace between the hairs should be large enough to contain the quantityof vapour which is required to complete the development of the copy.However, it should not be so large that the vapour which escapes fromthe copy can spread out, so that the contact between vapour and copy islost. It has been found that a space with favourable dimensions isobtained if the hairy surface is covered with the hairs having a lengthof 0.2-0.8 cm. Because such hairs are relatively limp, the copies canfreely expand and shrink during their passage through the apparatus.Because both walls move and cooperate with each other, which means thatthey touch each other when no copy material is present between them,there is no risk that the copy material will stick in the apparatus.

The walls between which the copies are heated can be.

stretched around guide rollers and driving rollers. In thelast-mentioned construction the zone between the cooperating parts ofthe belt can be heated with the aid of electrical radiators which aremounted along the path of the belts. Another attractive embodiment,however, is obtained when the belts contact stationary heating elements,which consist of box-like bodies through which heated air is passed.

An embodiment of the apparatus according to the invention, which is usedin combination with a developing apparatus for diazotype copies, isillustrated in the accompanying drawing in diagrammatic sectional view.

In the drawings, 1 is the developing section (which is of a knownconstruction, see United States patent specification No. 2,981,171) inwhich a thin layer of developing liquid is applied on to both sides ofthe copy material to be developed.

In this drawing:

FIG. 1 gives a section perpendicular to and through the axes of rollersdriving and guiding endless belts forming the moving walls according tothis invention, and

FIG. 2 gives a section through one of the boxes between said belts forheating by air, said section being taken along the line IIII in FIGURE 1but not showing the part of the box through which the section of FIGURE1 is taken. This FIGURE 2 is at a smaller scale than FIGURE 1, namelyabout half the scale of FIGURE 1.

The drying apparatus comprises three cooperating systems of endlessbelts. The first system consists of a number of juxtaposed belts 4,which have been stretched around a guide roller 5 and a driving roller6; the belts 4 are made of a fabric which does not absorb vapour and isheat-resistant, such as a fabric made of polyester yarn. The second beltsystem consists of a number of juxtaposed belts 7, which are made ofheat-resistant material having a soft hairy surface (such as nylonplush, the hairs of which have a length of 0.2-0.8 cm.) and which havebeen stretched around guide rollers 8, 9, 10 and 11 and around a drivingroller 12. The third belt system consists of a number of juxtaposedendless belts 13, which have been stretched around a guide roller 14 anda driving roller 15. The belts 13 are also made of a fabric which doesnot absorb moisture and is heatresistant. Each belt system may alsoconsist of one broad belt instead of being composed of a number ofjuxtaposed belts. All the belts are driven with the same velocity.

Between the belts, heating elements 16, 17 and 18 are mounted, withwhich the belts are in contact. In the apparatus shown in the figure,the heating elements consist of boxes formed of metal plate, throughwhich air having a temperature of about 120 C. is blown. The boxes 16and 17 have plane walls; the box 18 has a partly inclined, partly curvedwall as shown. The temperature of the air is regulated in a known mannerwith the aid of a thermostat 19 which controls the temperature of thewall of one of the boxes, e.g. box 17.

Furthermore the apparatus contains guide plates 20, 21, and 22, guiderollers 23 and 24 and a receiving table 25. 26 shows the feeding guideplate for copies exposed in a copying apparatus not shown. This plate 26guides the copies between the upturned edges of two baths 29 and 30 witha developing liquid, each with a rotating roller 27 and 28 respectivelypartially submerged therein. Thus the copies are guided into the nip oftwo rollers 31 and 32 moistened by developing liquid and from this nipthe copy sheets are guided by and between rollers 33 and 34 pushedtogether by a weighting roller 35.

Rollers 33 and 34 squeeze out surplus of developing liquid from the copysheets between them.

From these rollers the copy sheets are taken up by a driven guidingroller 36, which guides them to belts 4 on top of roller 6. Thus thebelts guide the copy sheets downwards between belts 4 and 7, the sheetsbeing thereupon guided around roller 8 by the guide plates extending onone side between the belts 4 and at the other side between the belts 13,so that the sheets are thereafter moved upwardly between belts 7 and 13,separated from the top of belts 13 on roller 15 by guide plates 21 andguided by guide plates 22 to the nip between guide rollers 23 and 24 soas to be discharged on receiving table 25. During this transport of thecopies between and in contact with belts 4, 7 and 13, the copies arequickly heated. The vapour thus formed cannot escape at once, but isretained in the copies and between the hairs of the belts 7. Theelevated temperature and the moist medium ensure that the developmenttakes place rapidly, so that it is practically entirely complete whenthe copies are fed around the roller 11 by the plates 20. The copies,while still damp, are then passed between the belts 7 and 13. Thesebelts have less intimate contact with each other owing to the curvaturein the wall of the box 18. Hence, the evaporated Water can now escapeand the copy is dried. The dried copy is then carried off by the belts13, guide plates 21, 22 and guide rollers 23 and 24 and delivered on tothe receiving table 25 as described.

The following rollers are driven positively from an external sourceincluding an electric motor with suitable gear mechanism not shown: 27,28, 36, 6, 12, 15 and 23. Gear wheels 37, 38, 39, 40 and 41 at one endof the apparatus connect rollers 6, 12 and 15 drivingly, a chain 42drives roller 23 from roller 12 and a chain 43 drives roller 36 fromroller 6. Rollers 31, 32, 33, 34, 35 and 24 are rotated by frictioncontact with driven rollers as shown. Rollers 5, 8, 9, 10, 11 and 14 areeach rotated by frictional contact with one of the belts 4, 7 and 13.Rollers 5 and 14 are loaded by springs 44 attached at their lower endsto the stationary structure and at their upper ends to end trunnions ofsaid rollers. These springs urge the rollers S and 14 downwardly to keepthe belts 4- and 13 under suflicient tension. Roller S is verticallyadjustable by set screws 45 adapted When rotated to move the roller 8with the guide plates 20 up or down by engaging the end trunnions ofthis roller 8. Rollers 5, 8 and 14 are movably guided for up or downmovement by guide slots 46 for their end trunnions.

FIGURE 2 shows a centripetal fan 47 driven through its shaft 48 by anelectric motor 49, mounted on top of a surrounding airtight casing 50.There could be one such casing 50 with fan 47 for the three boxes 16, 17and 18 in common, this casing extending the full width of the threeboxes together, but having internal guide walls necessitating all theair entering from the three boxes to pass the fan 47. These three boxesare extending backwards, as seen in FIGURE 1, to the outside of theapparatus, where there are no belts 4, 7 and 13, and the easing 50 issecured to the end of these boxes by bolts 51. Each of the boxes 16, 17and 18 is divided into an upper compartment 52 and a lower com artment53, which com partments are separated by a horizontal partition 54,which does only extend in those parts of the boxes outside the partscontacting the belts 4, 7 and 16. Thus the fan 47 is adapted tocirculate air through the fan downwards and to the left side as seen inFIGURE 2, being to the front as shown in FIGURE 1, Le. through lowercompartment 53, then upwards in the zone of the plane of FIGURE 1 andthen backwards as seen in FIGURE 1, i.e. to the right as seen in FIGURE2, in the upper compartment 52, and so back to the fan 47 again.Electrical heating means 55 governed by thermostat 19 heat thecirculating air to the required temperature. Curved walls 56 and 57(FIG. 2) guide the air smoothly to and from the fan 47.

What we claim is:

1. A process for drying damp sheet material which comprises, afterapplying liquid to sheet material to dampen the same, passing the dampmaterial between two walls which face one another, are moving togetherin the same direction and will hold the material between theirconfronting surfaces so as to transport it through a drying zone, andheating said damp material between said walls to evaporate moisture fromit in said zone, said walls being formed of material substantiallynon-absorptive to moisture and at least one of their confrontingsurfaces being a soft hairy surface engaging said sheet material throughlimp hairs which will keep evaporated moisture in contact with saidsheet material yet enable said sheet material to expand or shrink freelyas it is dried.

2. A process according to claim 1, wherein the sheet material consistsof damp photocopy print material.

3. A process according to claim 1, wherein the sheet material consistsof damp diazotype print material.

4. An apparatus for drying damp sheet material comprising, inassociation with means for applying liquid to sheet material that isthereafter to be dried, means including contiguous movable walls havingconfronting surfaces to receive and hold therebetween damp sheetmaterial being delivered from said liquid applying means, means formoving said Walls to transport said material through a drying zone, andmeans for applying heat to said material between said walls to evaporatemoisture from it as it is transported through said zone, wherein atleast one of said walls is formed of a material substantiallynon-absorptive to moisture and presents as one of said confrontingsurfaces a soft hairy surface engaging said sheet material through limphairs which will keep evaporated moisture in contact with said sheetmaterial yet enable said sheet material to expand or shrink freely as itis dried.

5. Apparatus according to claim 4, wherein the hairs of the hairysurface have a length of 0.2-0.8 cm.

6. An apparatus according to claim 4, said walls being constituted bycontiguous flights of endless belts, there being respective guiderollers and drive rollers around which said belts are stretched.

7. An apparatus according to claim 6, said heat applying meanscomprising stationary heating elements in the form of box-like bodiescontacting the inner sides of said endless belts and means for passingheated air through said box-like bodies.

8. An apparatus according to claim 6, said heat applying meanscomprising stationary heating elements in the form of box-like bodiescontacting the inner sides of said endless belts, means for passingheated air through said box-like bodies, and means including athermostat responsive to the temperature of a wall of one of saidbox-like bodies for regulating the temperature of said air.

9. An apparatus for drying damp photo-print sheet material comprising,in association with means for applying a thin layer of developing liquidto at least one side of exposed photoprint sheet material, meansincluding systems of endless belts having contiguous elongated flightspresenting confronting surfaces to receive and transport therebetweendamp sheet material being delivered from said liquid applying means,means for driving said belts so as to move said flights together withsaid material therebetween through a drying zone, and means for applyingheat to said material between said flights to evaporate moisture from itand complete the development of it in said zone, wherein the belts ofone of said systems are formed of a fabric that is substantiallynonabs-orptive to moisture and presents over its outer side as one ofsaid confronting surfaces limp hairs which will keep evaporated moisturein contact with said material yet enable said material to expand orshrink freely as it is dried.

10. An apparatus according to claim '9, the belts of said one systemhaving advance and return flights coacting respectively with contiguousflights of the belts of first and third endless belt systems locatedadjacent thereto, there being means for guiding said material from saidadvance flight to said return flight, said advance flight being heldsufficiently close to the coacting flight of said first belt system thatmoisture evaporated from said material will be kept by said hairs incontinuing contact with said material, and said return flight havingless intimate contact with the coacting flight of said third belt systemso that such moisture may escape.

References Cited UNITED STATES PATENTS 1,919,275 7/1933 Dunham 34203 X2,581,790 1/1952 Gates 23'79 2,895,395 7/1959 Gern 34-123 X 2,924,1632/1960 Jaffe et al.

3,145,637 8/1964 Franz -94 3,248,802 5/1966 Wagner 3495 3,263,345 8/1966Fleesher et a1.

" KENNETH w. SPRAGUE, Primary Examiner.

1. A PROCESS FOR DRYING DAMP SHEET MATERIAL WHICH COMPRISES, AFTERAPPLYING LIQUID TO SHEET MATERIAL TO DAMPEN THE SAME, PASSING THE DAMPMATERIAL BETWEEN TWO WALLS WHICH FACE ONE ANOTHER, ARE MOVING TOGETHERIN THE SAME DIRECTION AND WILL HOLD THE MATERIAL BETWEEN THEIRCONFRONTING SURFACES SO AS TO TRANSPORT IT THROUGH A DRYING ZONE, ANDHEATING SAID DAMP MATERIAL BETWEEN SAID WALLS TO EVAPORATE MOISTURE FROMIT IN SAID ZONE, SAID WALLS BEING FORMED OF MATERIAL SUSBTANTIALLYNON-ABSORPTIVE TO MOISTURE AND AT LEAST ONE OF THEIR CONFRONTINGSURFACES BEING A SOFT HIARY SURFACE ENGAGING SAID SHEET MATERIAL THROUGHLIMP HAIRS WHICH WILL KEEP EVAPORATED MOISTURE IN CONTACT WITH SAIDSHEET MATERIAL YET ENABLE SAID SHEET MATERIAL TO EXPAND OR SHRINK FREELYAS IT IS DRIED.